We did overestimate the savings for that specific greywater project. The estimate was also in reference to the removal of a 15'x15' bermuda grass lawn. Because the city of Tucson prices water on a sliding scale, the commenter is correct that a low water user would save very little by conserving water through a greywater system. However, a higher water user has even greater potential to save.

As a sample case, a household using a moderate-high amount of water, averaging 25CCF per month, would spend about $72 on water per month. If that homeowner hit our target 40% reduction in water use (the amount that the average homeowner uses on the landscape) down to 15 CCF/mo, the bill would reduce to $20/mo, for a $52/mo or $615/yr average cost savings. That 40% reduction is not hard to acheive, through recontouring the landscape to retain and infiltrate rainwater to support native plants which survive on rainfall, and. if necessary, watering higher water use plants such as fruit trees using greywater and rainwater stored in cisterns. New developments can achieve this target without significant (if any) added expense by incorporating this approach into the initial plans.

The State of Arizona also offers tax credits to anyone implementing rainwater harvesting or greywater systems, up to $1000 or 25% of the cost of the system. The State has only given out about half of these available funds over the last 3 years - most anyone who would apply would receive the credit.